Sulfide-Tolerant Catalysts And Methanol Oxidation Catalysts For Fuel Cells

Platinum is considered to be the most efficient catalyst in proton exchangemembrane fuel cells （PEMFCs）. But the content of Pt is so poor that leading to the costof fuel cell much expensive. Besides, the toxic gases, such as SO_x, NO_xand so on, existin fuel gas and air can cause the catalyst poisoned, which is the critical factor that causethe short life of fuel cell under working condition. High cost and short life restrict thedevelopment of fuel cell. The cumulative effect of catalyst poisoning is the major causethat leading to the short life of fuel cell. Therefore, how to promote the poisoningresistance of Pt catalyst under lower content is the critical way to solve the short life offuel cell.In the first part of this paper, we successfully deposit Pt particles on MoO₃/Csubstrate via hydrothermal method. Transmission electron microscopy （TEM）, X-raydiffraction （XRD）, and X-ray photoelectron spectrometry （XPS） were used tocharacterize the Pt-MoO₃/C catalyst. Na2SO3solution was used as the poisoning speciesto study the SO₂poisoning resistance by Autolab. The preliminary results show that:（1） We successfully prepared Pt-MoO₃/C catalyst by hydrothermal method. TEMresults show that the catalyst has smaller mean particle size about3nm compared withcommercial Johnson-Mathewy Pt/C catalyst. Besides, the Pt nanoparticles uniformlydispersed on the MoO₃/C substrate with no obvious agglomeration.（2） Pt-MoO₃/C catalyst has higher catalytic activity for oxygen reduction reactionthan commercial Johnson-Mathewy Pt/C catalyst. SO₂poisoning tests show thatPt-MoO₃/C catalyst also exhibits better SO₂poisoning resistance.（3） We also run the cyclic voltammetry to investigate the recovery performance ofthe catalysts. The results show that Pt-MoO₃/C catalyst also exhibits better recoveryperformance than commercial Pt/C catalyst.The direct methanol fuel cell （DMFC） has wide development prospect in portablepower source and electric automobile due to its advantages of reduced system weightand size, high energy efficiency and so on. Meanwhile, the lower catalytic activity formethanol oxidation and the methanol crossover phenomenon restrict the development ofDMFC. So far, Pt or Pt-based catalysts are the best catalysts for methanol oxidation. But,Pt is very expensive and easily poisoned by CO and CO-like intermediates betweenmethanol electro-oxidation, which can reduce the catalytic activity of catalyst. So, how to promote the CO toleration has been widely studied.In the second part of this paper, we prepare three kinds of the different atom ratioof Pt:Mo, respectively. TEM, XRD, and XPS were used to characterize the three kindsof catalysts. Liner sweeping voltammetry, pre-adsorbed CO monolayer stripping,coupled with cyclic voltammetrys were used to analysis the influence of different atomratio of Pt:Mo. The preliminary results show that:（1） The catalyst has the best catalytic activity for methanol oxidation when theatom ratio Pt:Mo is3:1. The catalyst exhibits better activity than commercial JM Pt/Ccatalyst, but still needs to be improved compared with commercial JM Pt-Ru/C catalyst.（2） CO stripping experiment show that the introduction of MoO₃could enhance theCO toleration ability of Pt-MoO₃/C catalyst.